| 摘要 |
Porous sheets are made from polymers and copolymers of vinyl chloride by sintering the powdered resin after first preheating it at a temperature lower than the sintering temperature for not less than 2 minutes. Preferred temperature ranges are 70-300 DEG C. for preheating and 160-350 DEG C. for sintering. Preferred compositions comprise a mixture of polyvinyl chloride and a copolymer of vinyl chloride containing at least 70% vinyl chloride, specified comonomers being vinyl acetate, vinylidene chloride, vinyl ethers of higher aliphatic alcohols and vinyl esters of higher aliphatic acids. Specified methods of preheating include heating with hot air. Preferred products are sheets of 0.8-0.3 mm. in thickness and 35-70% porosity.
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